Xen users - Mar 2007 - Building a xen Dom0 kernel for a very, very recent kernel branch

Hey, all,

This is mostly a request for a pointer to docs, I guess, since I
haven''t
had much luck finding any on my own that have been helpful...

I''m working on configuring a new machine to run Xen, but have found
myself needing to use the 2.6.21 kernel tree because of some bugfixes
that are only available there (as of 2.6.21-rc3).  

But, I''m having some trouble figuring out how to build my own xenified
kernel; I downloaded the 3.0.4 source release, and that seems quite
insistent that I should be using the 2.6.16 kernel...

Can anyone point me to docs that might have more detail about how to
build a xen kernel for a very recent kernel branch?

(I''m building on Fedora Core 6 as my base OS, but I imagine that
instructions for any distro will work fine...)

Thanks!

- Ian

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> Can anyone point me to docs that might have more detail about how to
> build a xen kernel for a very recent kernel branch?
I cannot fathom how the answer could be anything except something like
using a merge tool, but I''ll wait and listen to see what the gallery
has to say. :)

Joe.


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Kraska, Joe A (US SSA) wrote:
>> Can anyone point me to docs that might have more detail about how to
>> build a xen kernel for a very recent kernel branch?
>
> I cannot fathom how the answer could be anything except something like
> using a merge tool, but I''ll wait and listen to see what the
gallery
> has to say. :)
Which Linux? In the RedHat world, it''s often straifhtforward to take a
SRPM
and either update the source tarball, or apply clean patches from another 
source on the SRPM.

I''d work from an SRPM such as those at www.xensource.net or with the
Fedora
Core 6 distribution, if possible. 


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On Thu, Mar 22, 2007 at 05:48:38PM -0400, Marlier, Ian
wrote:
> Hey, all,
> 
> This is mostly a request for a pointer to docs, I guess, since I
haven''t
> had much luck finding any on my own that have been helpful...
> 
> I''m working on configuring a new machine to run Xen, but have
found
> myself needing to use the 2.6.21 kernel tree because of some bugfixes
> that are only available there (as of 2.6.21-rc3).  
> 
> But, I''m having some trouble figuring out how to build my own
xenified
> kernel; I downloaded the 3.0.4 source release, and that seems quite
> insistent that I should be using the 2.6.16 kernel...
> 
> Can anyone point me to docs that might have more detail about how to
> build a xen kernel for a very recent kernel branch?
Not a chance unless you are a very hardcore kernel hacker :-) The Xen code is
very intrusive into the heart of the kernel, so updating it to newer kernel
versions is non-trivial. For Fedora we have a guy who works *fulltime*
just doing forward ports of Xen to newer upstream kernel trees & even then
we''re typically 4-6 weeks behind upstream releases.
> (I''m building on Fedora Core 6 as my base OS, but I imagine that
> instructions for any distro will work fine...)
We just released a 2.6.20 + Xen 3.0.3 based kernel to FC6 updates-testing
if that''s any use:

http://download.fedora.redhat.com/pub/fedora/linux/core/updates/testing/6/

Work is underway to port it to 2.6.21 as well, but I can''t make any
promises
for when that''ll be released.

Meanwhile F7 is on 2.6.20 + 3.0.4, but this is not as stable as the FC6 3.0.3
based Xen tree is yet. By the time it is released in a couple of months F7
will probably be on 3.0.4 + 2.6.21, although if 3.0.5 comes out in the next
week or so we might skip 3.0.4 and go straight to 3.0.5 for F7.

Regards,
Dan.
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> This is mostly a request for a pointer to docs, I guess, since I
haven''t
> had much luck finding any on my own that have been helpful...
>
> I''m working on configuring a new machine to run Xen, but have
found
> myself needing to use the 2.6.21 kernel tree because of some bugfixes
> that are only available there (as of 2.6.21-rc3).
>
> But, I''m having some trouble figuring out how to build my own
xenified
> kernel; I downloaded the 3.0.4 source release, and that seems quite
> insistent that I should be using the 2.6.16 kernel...
>
> Can anyone point me to docs that might have more detail about how to
> build a xen kernel for a very recent kernel branch?
It''s highly non-trivial to do...

Thoughts:

if you only need domU support, the two most straightforward options are -
 * run it in an HVM guest if you have hardware that supports it
 * try out the paravirt_ops patchset jeremy fitzhardinge has been posting to 
LKML, which should be pretty close to applying cleanly with the latest 2.6.21 
code (can''t remember which rc patch it was most recently based against)

Depending on the fix you wanted, maybe you could backport that to a 
Xen-supported kernel if it''s not too complicated?  Likely to be easier
than
trying to forward port Xen dom0 support to 2.6.21!

Cheers,
Mrak


-- 
Dave: Just a question. What use is a unicyle with no seat?  And no pedals!
Mark: To answer a question with a question: What use is a skateboard?
Dave: Skateboards have wheels.
Mark: My wheel has a wheel!

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